In case Lawful Interception is active on a target subscriber or in case of Data Retention, it is a requirement for the Operator to provide location information available in the network as part of Intercept Related Information/Retained Data. In case the target subscriber is attached to an Evolved Packet System EPS through 3GPP access [3GPP TS 23.401, “General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access”], a Mobility Management Entity MME node is the node of the Evolved Packet Core which is the most location aware in the network. 3GPP LI Technical Specifications ([3GPP TS 33.107, “3G Security; Lawful Interception architecture and functions”], [3GPP TS 33.108, “3G Security; Handover interface for Lawful Interception (LI)”]) specify the LI architecture for 3GPP systems, including the EPS. According to [3GPP TS 33.107, “3G Security; Lawful Interception architecture and functions”], in case LI is activated for a target subscriber, the MME is required to report the following LI events, each one being related to a network procedure involving the target subscriber, to the Delivery Function DF2 (described below), including location information:                Attach        Detach        Tracking Area Update (TAU)        UE initiated PDN connectivity        UE initiated PDN disconnection        
These procedures may trigger one or several EPS bearer procedures: in such case, a Serving Gateway S-GW and a Packet Data Network Gateway PDN-GW are required to report the related signaling and, if required by the LI warrant, the Content of the Communication.
When the subscriber successfully attaches to the EPS network, the MME provides the User Equipment UE with a “Tracking Area List” which includes one or more Tracking Areas. When the UE moves inside the Tracking Area list, no Tracking Area Update TAU procedure is started by the UE.
In addition, when the UE successfully attaches to the EPS network, a default bearer is activated and, as part of the signaling, the PDN-GW may require (through the S-GW) the MME to report change of location for the involved subscriber. When this happens for a specific subscriber, each time that the MME detects a change of location due to a Tracking Area Update or any other network procedure involving the subscriber, the updated location is reported to the PDN-GW through the S-GW. This function, which is called MS Info Change Reporting ([3GPP TS 23.401, “General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access”], [3GPP TS 23.060, “General Packet Radio (GPRS); Service description”]), may be used e.g. for Location Dependent Charging.
FIG. 1A is part of the prior art and discloses an Intercept Mediation and Delivery Unit IMDU, also called Intercept Unit. The IMDU is a solution for monitoring of Interception Related Information IRI and Content of Communication CC for the same target. The different parts used for interception are disclosed in current Lawful Interception standards (see 3GPP TS 33.108 and 3GPP TS 33.107—Release 8). A Law Enforcement Monitoring Facility LEMF is connected to three Mediation Functions MF, MF2 and MF3 respectively for ADMF, DF2, DF3 i.e. an Administration Function ADMF and two Delivery Functions DF2 and DF3. The Administration Function and the Delivery Functions are each one connected to the LEMF via standardized handover interfaces HI1-HI3, and connected via interfaces X1-X3 to an Intercepting Control Element ICE in a telecommunication system. Together with the delivery functions, the ADMF is used to hide from ICEs that there might be multiple activations by different Law Enforcement Agencies. Messages REQ sent from LEMF to ADMF via HI1 and from the ADMF to the network via the X1_1 interface comprise identities of a target that is to be monitored. The Delivery Function DF2 receives Intercept Related Information IRI from the network via the X2 interface. DF2 is used to distribute the IRI to relevant Law Enforcement Agencies LEAs via the HI2 interface. The Delivery Function DF3 receives Content of Communication CC, i.e. speech and data, on X3 from the ICE. Requests are also sent from the ADMF to the Mediation Function MF2 in the DF2 on an interface X1_2 and to the Mediation Function MF3 in the DF3 on an interface X1_3. The requests sent on X1_3 are used for activation of Content of Communication, and to specify detailed handling options for intercepted CC. In Circuit Switching, DF3 is responsible for call control signaling and bearer transport for an intercepted product. Intercept Related Information IRI, received by DF2 is triggered by Events that in Circuit Switching domain are either call related or non-call related. In Packet Switching domain and Evolved Packet Switching domain the events are session related or session unrelated. While Lawful Interception is a real-time exercise, data from the past is used when Data Retention is practiced. FIG. 1B belongs to the prior art and shows the Handover Interfaces between a Data Retention System DRS (see ETSI DTS/LI-00033 V0.8.1 and ETSI DTS/LI-0039) at a Communication Service Provider CSP, and a Requesting Authority RA. The figure shows an Administration Function AdmF used to handle and forward requests from/to the RA. A Mediation and Delivery function MF/DF is used to mediate and deliver requested information. Storage is used to collect and retain all possible data from external data bases. The generic Handover Interface adopts a two port structure such that administrative request/response information and Retained Data Information are logically separated. The Handover Interface port 1 HIA transports various kinds of administrative, request and response information from/to the Requesting Authority and the organization at the CSP which is responsible for Retained Data matters. The HIA interface may be crossing borders between countries. This possibility is subject to corresponding national law and/or international agreements. The Handover Interface port 2 HIB transports the retained data information from the CSP, to the Requesting Authority. The individual retained data parameters have to be sent to the Requesting Authority at least once (if available). The HIB interface may be crossing borders between countries. This possibility is subject to corresponding national law and/or international agreements.
For a UE successfully attached to the Evolved Packet System EPS, the Tracking Area Update procedure is triggered only in case the UE moves outside the Tracking Area List. While this saves signaling in the network, in case of a Lawfully Intercepted target, after the attach procedure, the location is not reported to the LEMF until the next Tracking Area Update occurs, implying that the location can be considered known at the LEMF only at Tracking Area List level, i.e. with lower resolution than e.g. Cell identity.
The already existing MS Info Change Reporting procedure, which would allow the network nodes to provide more accurate location information in case of LI via Bearer modification procedure, is demanding from signaling point of view as it introduces additional signaling in the network and, unless already active for other reasons (e.g. location dependent charging), is not suitable to be activated generally (for all subscribers) for LI purposes, considering that normally only a few percentage of subscribers are target for interception. On the other side, invocation of this procedure only for subscribers who are targets for LI would introduce specific LI signaling in the network, which may allow detection of ongoing LI for specific subscribers.